The gravity station data (7102 records) were compiled by Professor Ervin. This data
base was received in April 1993. Principal gravity parameters include Free-Air Anomalies
and Simple Bouguer Anomalies (no terrain correction applied). The observed gravity
values are referenced to the International Gravity Standardization Net 1971 (IGSN
71). The gravity anomaly computation uses the Geodetic Reference System 1967 (GRS
67) theoretical gravity formula. The data are randomly distributed within the area
of central and northwestern Wisconsin north of 44 degrees north latitude.